This invention relates to fuel tank vent systems in diesel locomotives and, more particularly, to an improved fuel tank vent mountable under the locomotive carbody and capable of preventing fuel spills under normal locomotive operating conditions and also of preventing fuel tank damage due to overfilling.
It is common practice for a diesel electric railway locomotive to be provided with a large fuel tank supported beneath the locomotive underframe intermediate the trucks on which the underframe is carried. Such fuel tanks vary with the type and size of locomotive but commonly extend for substantially the width of the carbody and for varying lengths longitudinally thereof, up to twenty feet in one current model in which the fuel tank has a volume capacity of four thousand gallons of diesel fuel.
The fuel tank is connected to supply fuel to the locomotive engine in conventional fashion and includes one or more filler openings through which the tank may be filled at flow rates up to about four hundred gallons per minute by filling equipment provided at filling stations at various locations on the railroads. To avoid spillage, the filling nozzle is screwed or otherwise sealingly secured to the tank filler flange and the filling equipment is provided with automatic cutoff devices to turn off the flow of fuel when the tank reaches a filled condition, as indicated by a sudden rise in pressure.
In order to allow the filling and emptying of the fuel tank in normal use, it is commonly provided with a venting and pressure relief system opening through an upper surface of the tank to connect the interior of the tank with the atmosphere. The vent system is arranged to provide for free flow of air into or out of the tank and to prevent the spilling of any fuel from the tank through the vent under all normal locomotive operating conditions, including emergency stops. The vent also prevents damage to the tank due to overfilling by allowing the overflow of excess fuel should the automatic shutoff on the filling equipment fail to operate properly. The latter feature requires that the vent utilize relatively large openings and pipes on the order of two and a half inches diameter in order that excess fuel may pass out through the vent system at the rate delivered by the filling equipment without creating a pressure in the tank sufficient to deform its outer walls.
In the past, the vent requirement for a majority of diesel-electric locomotives has been met by the use of a long standpipe connected at a suitable point on the top of the tank, generally near one end, and extending upwardly at a suitable location to a point high enough to prevent fuel from reaching the top of the standpipe under all conditions of locomotive operation. The piping then turned downward, extending to a point beneath the carbody and outside the rails to conduct any overflow of fuel during filling to a suitable external point. In order to accomplish the aforementioned purposes, the standpipe was required to extend above the floor of the associated locomotive carbody and thus it was necessary to provide openings in the locomotive floor to accept the vent piping extending upwardly from the tank and downwardly again to a location below the locomotive underframe.